The present invention relates to room temperature curable silicone compositions useful for protecting polyurethane foam.
Polyurethane foam, by which it is meant herein foamed solids formed by the reaction of liquid isocyanate components with liquid polyol resin components, is an extremely useful material. In the construction industry, for example, it is often sprayed onto roofs, tanks, and other objects requiring protection or insulation. Polyurethane foam is easy and convenient to apply or install, is strong, and provides excellent thermal insulation. Unfortunately, most polyurethanes in use are rapidly and severely degraded by ultraviolet radiation. Ultraviolet radiation, having a wavelength of from 180 Angstroms to 3900 Angstroms, comprises a significant portion of the Sun's radiation. Care must therefore be taken to minimize or prevent the exposure of polyurethane foam to sunlight.
Silicones are well known for their resistance to degradation by ultraviolet radiation. Therefore, silicones of various descriptions have seen use as protectants for polyurethane foam. Since spraying is the preferred mode of applying a silicone coating over polyurethane foam, it is desirable that the silicone be sprayable. Heretofore, it has been necessary that the silicone be either diluted with solvent or provided in emulsion form so that it could be sprayed. The previously known polyurethane foam protecting silicones have not been entirely satisfactory.
For example, silicones applied at less than 80% by weight silicone solids, i.e. 20% solvent or water, tend to shrink as the solvent or water evaporates. The use of silicones containing 20% or more solvent also necessitates health, safety, and environmental precautions.
In addition, heretofore known polyurethane foam protecting silicones have been plagued by the adherence of dirt to the silicone coating and consequent degradation of appearance.
These problems have been solved by the compositions of the present invention and their use.
Related silicones are disclosed in U.S. Pat. No. 4,322,518, issued Mar. 30, 1982 to John Blizzard and assigned to the assignee of the present invention.